Physlets Illustrations

8.1
When the mass is changed, the momentum does not undergo any changes. When the force is applied for a longer amount of time, the momentum is also changed longer. This is shown by a force vs time graph.

8.2
When the mass is changed the kinetic energy changes. When mass is changed the speed also changes which alters the kinetic energy.

8.3
The forces are always equal and opposite. If one momentum decreases, the other must increase. Therefore, the sum of the impulses of the balls has to equal zero.